Genetic Engineering Questions and Answers – Reporter Genes

1. Promoter-probe vectors are used often. Choose the correct statement for these vectors.
a) They are used for identifying sequences that can function as promoter in vivo
b) It contains a reporter gene which contains its promoter along
c) The reporter gene is having a cloning site
d) After insertion of DNA into the cloning site, selection of plasmids is carried out by blue white screeningView Answer

Answer: a
Explanation: Promoter- probe vectors are used for identification of sequences that can function as a promoter in vivo. It consists of a reporter gene which is not having its promoter along but other genes such as those for chloramphenicol resistance are present. The reporter gene is preceded by the cloning site and after the insertion of DNA has been done, selection of plasmids is carried out by using chloramphenicol resistance.

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2. GFP is one of a marker which is used for screening libraries in hosts other than E. coli. Choose the incorrect statement for GFP.
a) It stands for Green Fluorescent Protein
b) It is obtained from a bio-luminescent jellyfish and produces protein aequorin which emits blue light
c) The blue light is produced because of binding of sodium ions
d) The absorbed blue light produces green light which can be detected furtherView Answer

Answer: c
Explanation: It stands for green fluorescent protein and is obtained from a bio-luminescent jellyfish. The jellyfish produces protein aequorin which produces blue light. This blue light is produced because of binding Calcium ions. The absorbed blue light emits green light which is detected further.

3. Luciferase genes are also used at times for detection. Choose the correct statement for them.
a) They are obtained from fire flies only
b) The detection requires provision of substrate which produces light
c) Enzymes such as beta-galactosidase requires substrate X-gluc to produce light
d) Lucifearse genes are preferred over fluorescent proteinsView Answer

Answer: b
Explanation: Luciferase genes are not obtained only from fire flies but also from bio-luminescent bacteria and a sea pansy. The section requires a substrate which produces light. Enzymes such as beta-galactosidase requires X-gal for the production of blue light. Fluorescent proteins are more preferable over these because they don’t require substrates like luciferase genes.

4. In case of promoter-probe vectors, the same or related species should be as a vector whose DNA is to be screened.
a) True
b) FalseView Answer

Answer: a
Explanation: For promoter-probe vectors, the same species should be used as a host for the vector whose DNA is to be screened. It is so because a gene which is a promoter in one species may not be a promoter in other gene and thus it becomes difficult to detect.

Answer: c
Explanation: There are some sequences which can function as origins of replication and they are known as autonomously replicating sequences (ARS). At times, the selection is carried out for these sequences.

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6. Screening is often carried out for a sequence that interacts with a protein for which already a clone is present. It is carried out in which host?
a) Bacterial host
b) Fungal host
c) Parasitic host
d) Yeast hostView Answer

Answer: d
Explanation: Screening is often carried out for a sequence that interacts with a protein for which already a clone is present. This type of screening is often carried out in a yeast host.

Answer: a
Explanation: The two hybrid-screening system is based on the fact that many transcriptional activators consist of two domains, the DNA binding domain and activation domain. The activator binds through the DNA binding domain to a sequence upstream of the gene under its control. The activation domain stimulates transcription.

8. For two hybrid systems, activation domains can be present in different proteins also rather than being on a single protein. A sequence encodes _______ protein for which we want to find an interacting protein.
a) prey
b) bait
c) binding
d) activationView Answer

Answer: b
Explanation: Bait protein is the name given to the protein for whom we are looking for an interacting protein. Bait protein is cloned adjacent to the DNA binding protein. The protein interacting with bait protein is called as prey protein and leading to activation of domains.

9. The transcription domain is ________ if some of the bait and prey proteins are non-specific in nature?
a) deactivated
b) activated
c) destroyed
d) may be activated or notView Answer

Answer: d
Explanation: If the bait and prey proteins are non-specific in nature, some of them might lead to activation of the transcription domain without the presence of another domain.

10. _____ should enter the cell in the case of activation of the reporter gene for two hybrid system.
a) Bait protein
b) Prey protein
c) Both bait and prey protein
d) Either one of themView Answer

Answer: c
Explanation: Both prey and bait proteins should enter inside the cell for activation of the reporter gene for two hybrid system. It is so because activation is based on the interaction of these two proteins.

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11. Protein-protein interactions such as in electron transport lead to activation of the reporter gene.
a) True
b) FalseView Answer

Answer: b
Explanation: Protein-protein interactions are weak interactions and thus they are not sufficient for the activation of the reporter gene.